Journal•ISSN: 0367-7540

# Journal of the Institution of Electrical Engineers - Part III: Radio and Communication Engineering

About: Journal of the Institution of Electrical Engineers - Part III: Radio and Communication Engineering is an academic journal. The journal publishes majorly in the area(s): Electrical impedance & Amplitude modulation. It has an ISSN identifier of 0367-7540. Over the lifetime, 97 publication(s) have been published receiving 2526 citation(s).

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01 Nov 1946-Journal of the Institution of Electrical Engineers - Part III: Radio and Communication Engineering

TL;DR: New methods of analysis, which involve some of the mathematical apparatus of quantum theory, are illustrated by application to some problems of transmission theory, such as direct generation of single sidebands, signals transmitted in minimum time through limited frequency channels, frequency modulation and time-division multiplex telephony.

Abstract: Hitherto communication theory was based on two alternative methods of signal analysis. One is the description of the signal as a function of time; the other is Fourier analysis. Both are idealizations, as the first method operates with sharply defined instants of time, the second with infinite wave-trains of rigorously defined frequencies. But our everyday experiences?especially our auditory sensations?insist on a description in terms of both time and frequency. In the present paper this point of view is developed in quantitative language. Signals are represented in two dimensions, with time and frequency as co-ordinates. Such two-dimensional representations can be called ?information diagrams,? as areas in them are proportional to the number of independent data which they can convey. This is a consequence of the fact that the frequency of a signal which is not of infinite duration can be defined only with a certain inaccuracy, which is inversely proportional to the duration, and vice versa. This ?uncertainty relation? suggests a new method of description, intermediate between the two extremes of time analysis and spectral analysis. There are certain ?elementary signals? which occupy the smallest possible area in the information diagram. They are harmonic oscillations modulated by a ?probability pulse.? Each elementary signal can be considered as conveying exactly one datum, or one ?quantum of information.? Any signal can be expanded in terms of these by a process which includes time analysis and Fourier analysis as extreme cases. These new methods of analysis, which involve some of the mathematical apparatus of quantum theory, are illustrated by application to some problems of transmission theory, such as direct generation of single sidebands, signals transmitted in minimum time through limited frequency channels, frequency modulation and time-division multiplex telephony.

1,155 citations

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01 Jan 1947-Journal of the Institution of Electrical Engineers - Part III: Radio and Communication Engineering

TL;DR: In this paper, the authors investigated the values of permittivity and permeability of a mixture consisting of a homogeneous material in which particles are embedded and found that the results refer to initial permeability.

Abstract: The paper investigates the values of permittivity and permeability of a mixture consisting of a homogeneous material in which particles are embedded. Formulae are found which are valid at high frequencies, so long as the size of the particle is small compared with the wavelength and the packing is not too great. Special cases treated are iron-dust cores and expanded dielectrics in which the "particles" are air bubbles. For ferromagnetic materials, weak fields only are assumed, so that the results refer to initial permeability. On account of the heterogeneity of the mixture, the permeability may become "lossy" (i.e. μ may be complex). Even when the substances are all non-ferromagnetic, the permeability of the mixture may depart from unity, or be complex.

236 citations

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01 Sep 1948-Journal of the Institution of Electrical Engineers - Part III: Radio and Communication Engineering

TL;DR: In this paper, it was shown that the broadside power gain is not a maximum when the amplitudes and phases of the elements are equal, unless the elements were ideal isotropic point-sources.

Abstract: It appears that it is possible to approximate as closely as desired to a specified radiation-pattern by a suitable distribution of field over an aperture of given size, though the necessary currents in the conducting elements of the source would in general be prohibitively large in comparison with the power radiated. The difficulty of obtaining a high degree of approximation, and in particular a power gain very much greater than that of a uniformly illuminated aperture, is thus a practical rather than a theoretical one. The same is true for the linear array of given length as for the continuous aperture if no limit is set to the number of elements. Even when this number is limited by the adoption of half-wavelength spacing, the broadside power gain is not a maximum when the amplitudes and phases of the elements are equal, unless the elements are ideal isotropic point-sources.

190 citations

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Philips

^{1}01 May 1946-Journal of the Institution of Electrical Engineers - Part III: Radio and Communication Engineering

138 citations

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01 Nov 1946-Journal of the Institution of Electrical Engineers - Part III: Radio and Communication Engineering

TL;DR: In this article, it was suggested that it is possible to transmit speech and music in much narrower wavebands than was hitherto thought necessary, not by clipping the ends of the waveband, but by condensing the information.

Abstract: It is suggested that it may be possible to transmit speech and music in much narrower wavebands than was hitherto thought necessary, not by clipping the ends of the waveband, but by condensing the information. Two possibilities of more economical transmission are discussed. Both have in common that the original waveband is compressed in transmission and re-expanded to the original width in reception. In the first or "kinematical" method a temporary or permanent record is scanned by moving slits or their equivalents, which replace one another in continuous succession before a "window." Mathematical analysis is simplest if the transmission of the window is graded according to a probability function. A simple harmonic oscillation is reproduced as a group of spectral lines with frequencies which have an approximately constant ratio to the original frequency. The average departure from the law of proportional conversion is in inverse ratio to the time interval in which the record passes before the window. Experiments carried out with simple apparatus indicate that speech can be compressed into a frequency band of 800 or even 500 c/s without losing much of its intelligibility. There are various possibilities for utilizing frequency compression in telephony by means of the "kinematical" method. In a second method the compression and expansion are carried out electrically, without mechanical motion. This method consists essentially in using non-sinusoidal carriers, such as repeated probability pulses, and local oscillators producing waves of the same type. It is shown that one variety of the electrical method is mathematically equivalent to the kinematical method of frequency conversion.

91 citations